//
//Copyright (c) 2015 Pedro Dal Col, Pliny Smith
//
public class HexUtil { 

    private static final Integer[] table = new List<Integer> { 
            0, 1996959894, -301047508, -1727442502, 124634137, 1886057615, -379345611, -1637575261,
            249268274, 2044508324, -522852066, -1747789432, 162941995, 2125561021, -407360249, -1866523247, 
            498536548, 1789927666, -205950648, -2067906082, 450548861, 1843258603, -187386543, -2083289657, 
            325883990, 1684777152, -43845254, -1973040660, 335633487, 1661365465, -99664541, -1928851979, 
            997073096, 1281953886, -715111964, -1570279054, 1006888145, 1258607687, -770865667, -1526024853, 
            901097722, 1119000684, -608450090, -1396901568, 853044451, 1172266101, -589951537, -1412350631, 
            651767980, 1373503546, -925412992, -1076862698, 565507253, 1454621731, -809855591, -1195530993, 
            671266974, 1594198024, -972236366, -1324619484, 795835527, 1483230225, -1050600021, -1234817731, 
            1994146192, 31158534, -1731059524, -271249366, 1907459465, 112637215, -1614814043, -390540237, 
            2013776290, 251722036, -1777751922, -519137256, 2137656763, 141376813, -1855689577, -429695999, 
            1802195444, 476864866, -2056965928, -228458418, 1812370925, 453092731, -2113342271, -183516073, 
            1706088902, 314042704, -1950435094, -54949764, 1658658271, 366619977, -1932296973, -69972891, 
            1303535960, 984961486, -1547960204, -725929758, 1256170817, 1037604311, -1529756563, -740887301, 
            1131014506, 879679996, -1385723834, -631195440, 1141124467, 855842277, -1442165665, -586318647, 
            1342533948, 654459306, -1106571248, -921952122, 1466479909, 544179635, -1184443383, -832445281, 
            1591671054, 702138776, -1328506846, -942167884, 1504918807, 783551873, -1212326853, -1061524307, 
            -306674912, -1698712650, 62317068, 1957810842, -355121351, -1647151185, 81470997, 1943803523, 
            -480048366, -1805370492, 225274430, 2053790376, -468791541, -1828061283, 167816743, 2097651377, 
            -267414716, -2029476910, 503444072, 1762050814, -144550051, -2140837941, 426522225, 1852507879, 
            -19653770, -1982649376, 282753626, 1742555852, -105259153, -1900089351, 397917763, 1622183637, 
            -690576408, -1580100738, 953729732, 1340076626, -776247311, -1497606297, 1068828381, 1219638859, 
            -670225446, -1358292148, 906185462, 1090812512, -547295293, -1469587627, 829329135, 1181335161, 
            -882789492, -1134132454, 628085408, 1382605366, -871598187, -1156888829, 570562233, 1426400815, 
            -977650754, -1296233688, 733239954, 1555261956, -1026031705, -1244606671, 752459403, 1541320221, 
            -1687895376, -328994266, 1969922972, 40735498, -1677130071, -351390145, 1913087877, 83908371, 
            -1782625662, -491226604, 2075208622, 213261112, -1831694693, -438977011, 2094854071, 198958881, 
            -2032938284, -237706686, 1759359992, 534414190, -2118248755, -155638181, 1873836001, 414664567, 
            -2012718362, -15766928, 1711684554, 285281116, -1889165569, -127750551, 1634467795, 376229701, 
            -1609899400, -686959890, 1308918612, 956543938, -1486412191, -799009033, 1231636301, 1047427035, 
            -1362007478, -640263460, 1088359270, 936918000, -1447252397, -558129467, 1202900863, 817233897, 
            -1111625188, -893730166, 1404277552, 615818150, -1160759803, -841546093, 1423857449, 601450431, 
            -1285129682, -1000256840, 1567103746, 711928724, -1274298825, -1022587231, 1510334235, 755167117};

    public static Integer CRC32Table(Blob data) 
    { 
        Integer[] intArr = EncodingUtil.convertToHex(data).getChars();
        data = null;
        Integer b = 0;
        Integer crc = -1;  //hexToInt('ffffffff');
        Integer size = intArr.size();
        
        for (Integer i = 0; i < size; i+=2)
        {
     
            b = ((intArr[i] & 15)+(intArr[i]>>>6)*9) * 16
              | (intArr[i+1] & 15)+(intArr[i+1]>>>6) * 9;
            crc = (crc >>> 8) ^ table[(crc ^ b) & 255];

        }

        // flip bits
        crc = crc ^ -1; //hexToInt('ffffffff');

        //System.debug('CRC32 = ' + intToHexLE(crc,4));// + '    ' + (crc & 4294967295L));
        return crc;
    }

    public static Integer CRC32Table(String hexStr) 
    { 
        Integer b = 0;
        Integer crc = -1;  //hexToInt('ffffffff');
        Integer size = hexStr.length();
        
        for (Integer i = 0; i < size; i+=2)
        {
     
            b = ((hexStr.charAt(i) & 15)+(hexStr.charAt(i)>>>6)*9) * 16
              | (hexStr.charAt(i+1) & 15)+(hexStr.charAt(i+1)>>>6) * 9;
            crc = (crc >>> 8) ^ table[(crc ^ b) & 255];

        }

        // flip bits
        crc = crc ^ -1; //hexToInt('ffffffff');

        //System.debug('CRC32 = ' + intToHexLE(crc,4));// + '    ' + (crc & 4294967295L));
        return crc;
    }
/*
    public static Integer CRC32Table(Zippex.FileObject fObj) 
    { 
        //String hexString = EncodingUtil.convertToHex(data);
        //Integer[] intArr = new List<Integer>();//fObj.fileData.getChars();
        //hexStr = null;
        Integer b = 0;
        Integer crc = -1;  //hexToInt('ffffffff');
        Integer size = fObj.fileData.length();
        
        for (Integer i = 0; i < size; i+=2)
        {
     
            b = ((fObj.fileData.charAt(i) & 15)+(fObj.fileData.charAt(i)>>>6)*9) * 16
              | (fObj.fileData.charAt(i+1) & 15)+(fObj.fileData.charAt(i+1)>>>6) * 9;
            crc = (crc >>> 8) ^ table[(crc ^ b) & 255];

        }

        // flip bits
        crc = crc ^ -1; //hexToInt('ffffffff');

        System.debug('CRC32 = ' + intToHexLE(crc,4));// + '    ' + (crc & 4294967295L));
        return crc;
    }*/

    //public static Integer CRC32Calc_slow (Blob data) 
    //{
    //    Integer crc = -1; //hexToInt('ffffffff');
    //    String hexString = EncodingUtil.convertToHex(data);
    //    //crc  = hexToInt('ffffffff');       // initial contents of LFBSR
    //    Integer poly = hexToInt('edb88320');   // reverse polynomial
    //    Integer b = 0;

    //    for (Integer j = 0; j < hexString.length()/2; j++)
    //    {
    //        b = hexToInt(hexString.substring(j*2, j*2+2));
    //        Integer temp = (crc ^ b) & hexToInt('ff');

    //        // read 8 bits one at a time
    //        for (Integer i = 0; i < 8; i++) 
    //        {
    //            if ((temp & 1) == 1) {
    //                temp = (temp >>> 1) ^ poly;
    //            } else {
    //                temp = (temp >>> 1);
    //            }
    //        }
    //        crc = (crc >>> 8) ^ temp;
    //    }

    //    // flip bits
    //    crc = crc ^ -1;//hexToInt('ffffffff');

    //    System.debug('CRC32 = ' + intToHexLE(crc,4));
    //    return crc;

    //}
    
    //Hex to Int Little Endian
    public static Integer hexToIntLE(String hexStr){
        //Long mask = 4294967295L; //FFFFFFFF
        Integer result = 0;

        for (Integer j = 0; j < hexStr.length(); j+=2){
            result |= (((hexStr.charAt(j  ) & 15)+(hexStr.charAt(j  )>>>6)*9)) << (4*(j+1));
            result |= (((hexStr.charAt(j+1) & 15)+(hexStr.charAt(j+1)>>>6)*9)) << (4*(j  ));
        }

        //return (result & mask); //remove sign from int
        return result;
    }

    //Int to Little Endian Hex
    public static String intToHexLE(Integer decNumber, Integer sizeInBytes)
    {
        String[] hexValues = new List<String>{'0','1','2','3','4','5','6','7','8','9','a','b','c','d','e','f'};
        String hexStr = '';
        Integer byteLocation = 0;

        while (decNumber != 0 && hexStr.length()<sizeInBytes*2)
        {
            hexStr += hexValues[(decNumber>>>4) & 15] + hexValues[decNumber & 15];
            decNumber >>>= 8;
            byteLocation++;
        }

        hexStr += '00'.repeat(sizeInBytes-byteLocation);

        return hexStr;
    }
}